1. Field of the Invention
The present invention relates to a process for producing 2-butynenitrile, as well as to a process for industrially producing, from the 2-butynenitrile produced by said process, 5-amino-3-methylpyrazole which is a useful intermediate for production of medicines, agricultural chemicals and photographic chemicals.
2. Description of the Prior Art
For production of 2-butynenitrile, there has been known a process which comprises producing 3-bromo-3-butenonitrile from 2,3-dibromopropene and prussic acid and then reacting 3-bromo-3-butenonitrile with sodium carbonate [Compt. Rend., 253, 676 (1961) and 255, 3424 (1962)].
This process, however, produces 3-bromo-3-butenonitrile (a starting material for 2-butynenitrile) in low yield (26%) [Compt. Rend., 253, 676 (1961)] and has not been sufficient as a process for industrially producing 2-butynenitrile.
For production of 5-amino-3-methylpyrazole, there has been known a process which comprises producing 5-amino-3-methylpyrazole using 3-aminocrotononitrile as a starting material (JP-A-2-279674).
This process, however, has not been sufficient as a process for industrially producing 5-amino-3-methylpyrazole because the process uses a reagent having a risk of producing fire, that is, 3-aminocrotononitrile as a starting material is obtained by a method (disclosed in, for example, JP-A-2-134354) of reacting acetonitrile with a stoichiometric amount of an alkali metal or the hydride thereof (both of them generate hydrogen when contacted with water).
The present inventors found that 2-butynenitrile can be obtained in high yield, without using any reagent having the above-mentioned problem, by using a process comprising a step of cyanogenating 2,3-dichloropropene of good industrial availability to produce at least one intermediate selected from the group consisting of 3-chloro-3-butenonitrile and 2,3-butadienenitrile. The present inventors further found that the reaction of the thus obtained 2-butynenitrile with hydrazine gives 5-amino-3-methyl pyrazole in high yield. The finding has led to the completion of the present invention.